To develop experimental animal models for human cancers of childhood, and to use these models to study the greater sensitivity of fetal and neonatal animal tissues to chemical carcinogens, and the role of factors other than the carcinogens themselves in enhancing or suppressing chemical carcinogenesis in experimental animals during intrauterine life and infancy. These include intensive studies on the nature of neurogenic tumors in rodents and the response of a subhuman primate species, Erythrocebus patas, to transplacental chemical carcinogens.